[Galwegian]

Here is my noob effort at explaining a value bet.
Let p=probability of winning the pot and
n=numbr of callers that you expect.
If (n+1)p > 1 then your bet is a value bet.
That is if (n+1)p>1 then you expected share
of the bet plus all the calls is bigger than
your bet.

Example: Say you have A[img]/images/graemlins/spade.gif[/img]K[img]/images/graemlins/diamond.gif[/img], get a preflop caller and the board is 3[img]/images/graemlins/heart.gif[/img]9[img]/images/graemlins/heart.gif[/img]A[img]/images/graemlins/club.gif[/img]5[img]/images/graemlins/spade.gif[/img] after the turn. Say that you're sure that your single opponent has a flush draw (based on your knowledge of his play). Then you have about 80% chance of winning at a showdown. So p=0.80. So any bet that you expect to get called by a flush draw has value here
(1+1)0.8=1.6>1. (In fact for every dollar you bet that you expect to be called you will get 1.6 dollars back)

Of course your bet sizing here should take other factors into consideration such as your equity in the existing pot. If the hand was just checked down then your expected share of the existing pot is 80%. A bet that you think will be called by a flush draw doesn't increase your equity in the existing pot. However a bet that wins the pot right there increases that equity to 100%. So the question is, can you get more that 20% of the existing pot from a value bet? If you think that the answer is yes then the value bet is +ev, if no then bet big enough to make him fold.